Development of an efficient procedure for preparation of islet tissue from human and animal pancreata that will allow tissue from the single donor only to be curative when transplanted to one or more diabetic recipients is a major objective of the proposed research. Physical separation of islets from exocrine tissue results in poor yield from both human and animal pancreata. In rats, dispersed neonatal pancreas can be transplanted without separation of islets and exocrine tissue. Depletion of exocrine enzymes coupled with dispersal only of adult pancreas could increase the quantity of islet tissue available for transplantation. Preliminary experiments indicate that under certain conditions short-term tissue culture of dispersed adult pancreatic tissue promotes selective survival of islet tissue while depleting or inactivating exocrine digestive enzymes. We will define the conditions necessary for short-term tissue culture to most efficiently purify islet tissue. Other approaches to prepare islet tissue for transplantation include use of pharmacological agents selectively deleterious to adult pancreatic exocrine cells and dispersal of the exocrine-enzyme-poor neonatal pancreas by the least destructive techniques. The ability of dispersed islet tissue prepared by these techniques to ameliorate diabetes will be tested by transplantation in rats and dogs. The duration of warm and cold ischemia tolerated by islets and the feasibility of islet preservation by cryogenic techniques will be investigated. Mechanisms responsible for the development of secondary lesions in diabetic rats will be studied by observing the effect of islet transplantation on the progression of retinopathy and on the ability of the glomerular mesangium to process macromolecules. New methods to prevent rejection of islet allografts will be studied in the rats. These include the use of a new drug (Oxisuran); donor antigen pretreatment; treatment of donor tissue with plant lectins; and culture of donor tissue prior to transplantation. The influence of anti-insulin antibodies and the distribution of islet tissue on the outcome of transplantation will be determined. Hormone biosynthesis and secretion will be studied in isolated human islets, and a large molecular weight protein tentatively identified as a glucagon precursor will be characterized.